1. Technical Field
The present invention relates generally to cellular wireless communication networks; and more particularly to the network infrastructures of such a cellular wireless communication networks.
2. Related Art
Cellular wireless networks include a xe2x80x9cnetwork infrastructurexe2x80x9d that facilitates wireless communications with wireless mobile terminals operating within a corresponding service coverage area. The network infrastructure couples to other networks, e.g., the Public Switched Telephone Network (PSTN), the Internet, etc, to support communication between the mobile terminals and the other networks. The wireless mobile terminals operating within a service coverage area of the network infrastructure wirelessly communicate with base stations of the network infrastructure. The network infrastructure routes the communications between the base stations and other mobile terminals and to terminals coupled to the other networks as well.
Wireless interface standards have been promulgated to standardize wireless communications between the mobile terminals and the base stations of the network infrastructure. Wireless interface standards include, for example, the Advanced Mobile Phone Service (AMPS) standards, the Global System for Mobile telecommunications (GSM) standards, the Code Division Multiple Access (CDMA) standards and the Time Division Multiple Access (TDMA) standards. Generations of these standards are generally referred to as first generation (1G), second generation (2G), third generation (3G), fourth generation (4G), etc. Each advancing generation of standards typically supports a greater number of services, a greater number of features, and provides better communication qualities. Resultantly, network infrastructures supporting these superior service offerings must provide increased performance levels, both from a network infrastructure perspective and from a wireless link perspective.
To increase performance within the network infrastructure, components having greater processing capability are deployed. For example, a newer MSC (or equivalent network components within an IP based network infrastructure) has capacity to service a far greater number of calls (and other services) than older MSCs. Further, the topology of the network infrastructure may also be altered to offload some service functions from one network infrastructure component to a plurality of network infrastructure component.
Increasing wireless link capacity is a much more difficult problem to solve. Because allocated frequency spectrum is fixed for a given wireless communication system deployment, improvements that increase wireless link capacity within the service coverage area must fit within this limitation. One common solution used to increase overall wireless link capacity within a service coverage area is to subdivide cells into smaller components, i.e., sectors. Currently deployed cells are now typically subdivided into three sectors. To further increase the wireless capacity of each cell, the cell may be divided into six, or more sectors. In each of these configurations, a single base station services all of the sectors of the cell. Complex antenna and processing structures are then required to support the wireless terminal traffic within the sectors.
Another solution to increasing wireless link capacity within a service coverage area is to deploy additional base stations. In the new deployment, a plurality of base stations, each serving a respective cell, service the geographic area that was previously serviced by a single base station. Base stations, including a Base Transceiver Subsystem (BTS), an antenna and a link to other network infrastructure components, e.g., a Base Station Controller (BSC) are both expense to acquire and expensive to deploy. Simply acquiring a location for the deployment of the base station, particularly in highly congested areas, is an expensive undertaking. In some urban areas, locations of sufficient size at which to deploy base stations may be nearly impossible to acquire. In these cases, the cost of the location may be exorbitant, but a cost that the service provider has not choice but to pay.
Further, the greater number of base station deployments increases network infrastructure operating complexity. In systems that subdivide the allocated frequency spectrum, e.g., TDMA systems, frequency reuse complexity and inter-cell interference problems increase with an increased number of deployed base stations. In systems that share spectrum among mobile terminals, e.g., CDMA (IS-95, IS-2000, WCDMA, GSM-2000, etc.), the noise floor increases for all mobile terminals. Further, in both CDMA and TDMA systems, the number of handoffs increases with the number of base stations. An increased number of handoffs during any given communication significantly increases both the processing requirements placed on the network infrastructure and the likelihood of dropped calls.
Thus, there is a need in the art for improvements in network infrastructure that result in increased wireless link capacity, that require fewer network infrastructure components, that reduce the complexity of operation of the network infrastructure, and that simplify handoff operations.
Thus, to overcome the shortcomings of the prior systems, among other shortcomings, a wireless communication system infrastructure of the present invention services wireless communications for mobile terminals operating in a service coverage area and includes a digital enclosure and a plurality of radio enclosures. The digital enclosure includes a plurality of wireless communication processing components that perform digital processing functions. The plurality of radio enclosures couple to the digital enclosure via communication links and each service wireless communications within a corresponding geographic area of the service coverage area. During operation of the wireless communication system infrastructure, two radio enclosures of the plurality of radio enclosures share a communication processing component of the digital enclosure while jointly servicing a single wireless communication.
The two radio enclosures reside at respective geographic locations that are separated by a geographic distance such that each of the radio enclosures services a respective cell. Further, each of the radio enclosures may service a plurality of sectors that form the cell. The digital enclosure couples to a base station controller, which in turn couples to a mobile switching center and, in some embodiments, to the Internet. Further, the mobile switching center couples to the public switched telephone network. In combination, these elements service the wireless communication.
The digital enclosure includes a core, a plurality of channel element modules coupled to the core, a control module coupled to the core, and additional components required for servicing the wireless communication. The core couples the control module and a channel element of a channel element module to at least one radio enclosure to service the wireless communication. During handoff of the wireless communication in a CDMA system from a first cell to a second cell, the core couples a channel element of the channel element module to a plurality of radio enclosures, each of which services a cell/sector(s) participating in the handoff. In one handoff operation in which six-way handoff is performed, the core couples a channel element of a channel element module within a channel element module of the digital enclosure to three radio enclosures. In this a handoff scenario, the channel element is coupled to two radio modules in each of the three radio enclosures, the two radio modules servicing two sectors participating in the handoff. Thus, a single channel element is used to service a wireless communication where three channel elements (in three separate base stations) would be required in prior systems.
Thus, the system of the present invention provides many important advantages and efficiencies over prior systems. By pooling digital communication processing elements (such as channel element modules, cores, control modules, and other digital communication processing elements) among multiple radio enclosures, system resources are more efficiently used. Thus, as contrasted to prior systems, additional wireless communications may be serviced according to the present invention using the same number of digital communication processing elements.
According to the present invention, only the radio enclosures need be deployed at a cell site. By reducing the equipment deployed at the cell site, the cell site occupies a smaller mechanical footprint. Such reduction reduces the lease cost for the cell site. Further, because of the smaller required mechanical footprint area, cell sites may be deployed at locations that were previously not sufficiently large for cell deployment.
Further, because the radio enclosures do not include digital communication processing elements, they are functionally simpler and, resultantly, simpler to deploy, configure, and commission. Moreover, by using digital enclosures that service a plurality of radio enclosures, the wireless communication system infrastructure is more cost effective to deploy and easier to expand. Such reduced costs in expansion are particularly important when backhauling systems for multiple carrier applications.
Moreover, other aspects of the present invention will become apparent with further reference to the drawings and specification, which follow.